The insulting U.S. meaning “black person” was in use by 1837, said to be from barracoon (by 1837), from Portuguese barraca “slave depot, pen or rough enclosure for black slaves in transit in West Africa, Brazil, Cuba.” No doubt the word was boosted by the enormously popular blackface minstrel act Zip Coon (George Washington Dixon) which debuted in New York City in 1834. But it is perhaps older (one of the lead characters in the 1767 colonial comic opera “The Disappointment” is a black man named Raccoon). Coon's age is 1843, American English, probably an alteration of British a crow's age.